Angelique Duet is a spin-off of the first Angelique game and one of the titles made to celebrate Koei's twentieth year anniversary. According to Ruby Party commentary, this title answered popular fan demand for an option to play as the first protagonist's rival, Rosalia.

he general gameplay and the characters of the original game return with the following changes:

-The player can choose Rosalia or Angelique as their protagonist. Romance events for the latter have been altered to distinguish itself from its base.
-Gift giving and written date invitations —features which were introduced in Special 2— have been implemented into this title with the same conditions and costs.
-When the protagonist visits their continent, she may receive ingredients for baking desserts. She can use them to create a dessert and give it as an alternative gift to guardians. She must give the baked goods before they expire.
-Friendship events between Angelique and Rosalia exist. Special 2's unique dating events with Sacred Guardians are included with additional night dates. The new events in this title include illustrated still images which change based on the protagonist.
-A different animated introduction sequence from Special is available. Special events and endings are presented as animated and voiced movie clips. Audible greetings from highly Intimate guardians are included.
-Stock quotes were rewritten for the main cast.
-Character portraits and backgrounds receive a graphical update.